Stuart Evans

Bob Barkany / Getty Images for TIME

Novacem could nearly erase the enormous carbon footprint of the $180 billion cement industry, which accounts for more than 5% of greenhouse-gas emissions  worse than the airlines. "Our goal is to become the first great cement company of the 21st century," says CEO Stuart Evans, 60. Cementmaking requires tons of carbon-emitting fossil fuels like coke to heat kilns above 1400°C. As its raw material, limestone (calcium carbonate), breaks down, carbon leaches from it. Chief scientist Nikolaos Vlasopoulos, 30, invented a method that replaces limestone with a family of carbon-free minerals called magnesium silicates. The raw material emits no carbon and cooks at just 700°C. Vlasopoulos says his product emits 85% less carbon than cement does. In the right situation, it even absorbs atmospheric carbon during production  making it "carbon negative." Novacem's product has half the strength of the strongest limestone-based cement, which means it works for many purposes but not for, say, a long, complex bridge. "We'll get there in the next couple of years," says Evans.